This study encompasses the following: Characterization of hemoglobin from individuals who are thought to have sickle cell anemia of a variant atypical mild form and/or unusually long survival. Elucidation of structure-function interrelationship of alpha and beta polypeptide chains in the sickling phenomenon as revealed by other naturally selected (genetic) amino acid substitutions found in association with the presence of homozygous beta super S chains. Chemical modification of hemoglobin S as a potential treatment of Sickle Cell Disease. Characterization of Hemoglobin S obtained during clinical trials of therapy for sickle cell vaso-occlusive crisis and correlation of the clinical and chemical data.